High Pressure Double Membrane Pump and Membrane Element for Such a Pump

ABSTRACT

A high pressure double membrane pump has a central housing ( 3 ), two cylindrical pump chambers ( 7,8 ), a coupling rod ( 4 ) which moves back and forth when the pump is in operation and which has a pump piston ( 9 ), two membranes which divide each of the pump chambers ( 7,8 ) into a product chamber ( 11,12 ) and a compressed air chamber ( 1,2 ) with changing volumes of which the membranes have a peripherally mounted membrane body ( 15 ). In the central area of the membrane body ( 15 ) a rigid implant body ( 17 ) is embedded which is equipped with a dog ( 18 ) which is connected to one end of the coupling rod ( 4 ), and a pneumatic control unit for the alternating impinging of compressed air upon the compressed air chambers. In the area of the compressed air chambers ( 1,2 ) a rigid supporting ring ( 20 ) is pushed onto the dog ( 18 ) between the end of the coupling rod ( 4 ) and the inner side of the membrane ( 5 ). The diameter of said supporting ring is between 50% and 95% of the diameter of the working surface of the membrane ( 5 ), and the periphery thereof is formed as a rounded shoulder ( 21 ) facing away from the membrane body ( 15 ).

The invention relates to a high pressure double membrane pump, equipped with

-   -   a central housing,     -   two cylindrical pump chambers,     -   a coupling rod which moves back and forth during pumping         operations having a pump piston,     -   two membranes which divide each of the pump chambers into a         product chamber and a compressed air chamber, provided with         divided membranes changing volumes, having a peripherally         mounted elastomer membrane body, wherein a rigid implant body is         embedded in the central region of the membrane body, which is         provided with a dog connected with one end to the coupling rod,         and     -   a pneumatic control unit for alternating impinging of compressed         air upon the pressure chambers.

The invention further also relates to a membrane element for such a double membrane pump.

A membrane pump of the type described above, wherein the invention is limited only to the special membrane, is described in DE 94 06 216 U1.

This membrane is provided with a disk-shaped implant body having a diameter which is relatively small when compared to the total membrane diameter.

It has been shown that in membrane pumps which have a transmission ratio of the input pressure of the compressed air to the output pressure of the supplied medium higher than 1:3, the known and customarily used membranes are subjected to a high stress. In particular in the intermediate region between the outer clamping point and the periphery of the implant body, elastomer raw materials are squeezed or milled and subjected to a high stress, so that after a short time, rupturing of the membrane occurs and the pump breaks down.

Therefore, the objective is to significantly increase the service life and the number of the strokes which can be realized by the membrane, without significantly reducing the pressure ratio of 1:3 or more.

This objective is achieved with a double membrane pump of the type described in the introduction, as well as with a membrane element, which are characterized in that in the region of the compressed air chamber, a rigid supporting disc is pushed onto the dog between the end of the coupling rod and the inner side of the membrane, which is provided with a diameter corresponding to between 50% and 95% of the diameter of the working area of the membrane and whose periphery is formed as a rounded shoulder facing away from the membrane body.

The supporting disc prevents excessive tilting of the membrane and thus it prevents an excessively massive asymmetric deformation of the surface of the membrane. In particular, the rounded shoulder of the supporting disc absorbs one component of the excessive deformation of the membrane and supports the membrane, without substantially reducing the efficiency of the pump. The compression ratio of such a membrane is therefore not limited in this manner.

For example, the diameter of the supporting disc is between 70 and 85% of the diameter of the working surface of the membrane. The supporting disc should not fill up the entire working surface. The diameter of the supporting disc should be also greater than the diameter of the implant body.

The supporting disc is preferably not firmly connected with the membrane. It is preferably provided with a central hole which has a diameter that is preferably greater than the diameter of the dog, so that movement is allowed along the axis of the dog in the direction of the movement axis of the coupling rod.

The form of the shoulder will depend also on the form of the membrane. Preferably, the shoulder starts from a smooth central area of the supporting disc and it is extended in its profile outward in a partial circle. At the same time, the partial circle is preferably rounded in such a way that—seen in profile view—it creates a tangent to the inclined surface which forms in its end point an angle of 20 to 60° to the movement axis of the coupling rod.

It is customary with membranes which are commonly used that the membrane is formed in the shape of a saucer which is curved toward the air chamber, in which case it is preferable when the supporting disc is inserted in the concave area of the curved membrane so that the outer ring area of the membrane can press on the shoulder when it is impacted by pressure.

A suitable material for the supporting disc is metal, preferably stainless steel or nickel-plated steel. However, it is also possible to manufacture the supporting disc from a very strong, web reinforced plastic material. It is essential that the supporting disc be much more rigid and non-elastic relative to the material of the membrane outside of the implant body.

The supporting disc can be provided with various forms, in particular also with a polygonal design. Cutouts or material reductions can be also used.

In particular, the membrane should be smooth on the outer side of the supporting disc which is visible in order to provide a bearing surface which is as large as possible.

Other dependent claims relate to the membrane element as such, which is also an object of the present invention.

A more detailed explanation is provided below based on the attached drawings. The drawings show in particular the following:

FIG. 1 a schematic representation of a section of a high pressure double membrane pump according to the invention;

FIG. 2 a cross-sectional view of a membrane element of a double membrane pump according to FIG. 1;

FIG. 3 an illustration of important parts of the double membrane pump according to the invention which are shown in the separated state.

The high pressure double membrane pump shown in FIG. 1 is operated with compressed air, which can be supplied for example with an excess pressure of 5 bar from a compressor and furnished via a pneumatic control unit (not shown here) to certain elements of the double membrane pump—in a manner which per se is known.

The high pressure double membrane pump is provided with a central housing 3, having in its center a coupling rod 4 which moves back and forth during the operation of the pump and which is provided with a pump piston 9. The coupling rod 4 is sealed relative to the central housing 3. The pump piston 9 is controlled so that its direction can be changed, and at the same time alternately impinged by air pressure from both sides.

The coupling rod 4 connects two mirror-symmetrically arranged membranes 5 and 6. In accordance with a system of membrane pumps, each of the membranes 5 and 6 is divided into a pump chamber 7, 8 which have a changing volume, and into a product chamber 11, 12, and a compressed air chamber 1, 2. Accordingly, the membrane 5 shown in FIG. 1 is indicated in the suction position, and the other membrane 6 is indicated in the pressure position. The membrane body is made of an elastomer and it is peripherally clamped as one can see from FIG. 1. For this purpose, the membrane 5 is provided on its periphery with a thickened edge bead 10.

FIG. 2 shows a cross-sectional view of the membrane 5. The main part of the membrane, which is formed by the elastomer membrane body 15, is comprised for example of two layers 15.1 and 15.2, specifically a main layer 15.1, which is made of a rubber material, and a protective layer 15.2, which is relatively thinner compared

to the main layer and which is made of PTFE plastic material.

In the central area of the membrane body 15 is embedded a rigid implant body 17 which is provided with a threaded dog 18. This threaded dog is connected with one end of the coupling rod 4. The implant body 17 fills up only one central area of the membrane body 15.

In the embodiment example, the implant body 17 is provided with a diameter which corresponds to 10 to 20% of the diameter of the membrane body 15.

It has been shown that a faster wear and tear occurs during the operation of a high pressure membrane pump which has a transmission ratio of 1:3 and higher. Rupturing and other defects occur in the area of the peripheral connection of the membrane, because as a result of the squeezing or milling and “blowing up” of the membrane in the area which is subjected to a high stress, the status of this area will deteriorate after a short time. The same phenomenon does not occur during operations with a transmission ratio of 1:1 between the compressed air and the product pressure. However, if the ratio was increased for example up to 1:3 due to the relationship between the size of the pistons and of the active surface area of the membrane, many ruptures and cracks quickly appeared, which in turn led to inoperability of the pump.

A substantial improvement of the lifespan is achieved with a supporting disc 20, which is pushed onto the dog in the area of the membrane 5 on the side turned toward the compressed air. The supporting disc 20 has a diameter D which in the embodiment example corresponds to about 80% of the diameter of the working area of the membrane 5, wherein this relationship can be preferably varied in a range between 50% and 90%. In any case, the diameter of the supporting disc 20 is smaller than the diameter of the working surface area of the membrane.

The diameter of the supporting disc 20 is greater than the diameter of the disk-shaped surface of the implant body 17, i.e. it corresponds to about 150% to 210% of the diameter of the implant body 17.

The supporting disc 20 is normally provided with a closed construction, which is provided only with one central opening. However, this does not exclude the option of cutouts or material reductions. The supporting disc is smooth on the side which is showing the membrane 5. In the present case, the supporting disc is manufactured either from stainless steel or from a steel material which has a surface that is plated with nickel. The supporting disc is circular in the present embodiment example. However, the option of a polygonal or a star form is not excluded.

An essential requirement is that the supporting disc 20 must have a periphery that is provided with a rounded shoulder 21 which is facing away from the membrane body 15.

As one can see from FIG. 2, the supporting disc is provided with a flat central area 23, which has a central opening 22. In the profile indicated in the illustration, the surface continues from the central area 23 to the edge in a partial circular or curved section on the shoulder 21. However, the partial circular or curved section does not end at right angle to the level of the flat central area; instead, it ends in an inclined surface, which—seen in profile—has a tangent T in its end point which forms an angle in the range from 20 to 60° to the movement axis A of the coupling rod 4.

As one can see from FIG. 1, when the membrane body 15 is formed in the shape of a saucer so that it is curved toward the air chamber, the supporting disc 20 can be inserted in the concave area of the membrane curve so that the outer ring area of the membrane presses onto the shoulder 21 when impacted by pressure.

The membrane body 15 is thus supported when a significant pressure is exerted onto the body. The outer area of the membrane body 15 is not deformed too strongly. However, during a counter-movement, wherein the membrane body is released from the supporting disc 20 which lies loosely on the threaded dog 20, the membrane 5 can assume the form which is optimal given the existing pressure conditions.

The rigidity, determined by a certain position of the membrane element 100 which consists of the membrane and the supporting disc 20, prevents unnecessary milling and pressure load in the milling region W. The member body 15 also requires the removal of a smaller amount of milling heat, which also works against material fatigue.

FIG. 3 shows an exploded view of essential components which belong to the invention. The outer limits of the pump chambers are formed by the pump covers 31, 32. In the pump area are arranged membranes 5, 6, which are provided with a supporting disc 20 placed upon them. The central housing 3 of the pump is equipped with the pump piston 9 which has the coupling rod 4 arranged in its center. The end is formed by the pump cover 32.

On the other hand, the end wall 33 limits the pump area in which the membrane 6 is moved with the supporting membrane 6. 

1-21. (canceled)
 22. A high pressure double membrane pump, equipped with: a central housing (3); two cylindrical pump chambers (7, 8); a coupling rod (4) which moves back and forth during pumping operations having a pump piston (9); two membranes which divide each of the pump chambers (7, 8) into a product chamber (11, 12) and a compressed air chamber (1, 2), provided with dividing membranes (5, 6) changing volumes, having a peripherally mounted elastomer membrane body (15), wherein a rigid implant body (17) is embedded in the central region of the membrane body which is provided with a dog (18) which is connected with one end of the coupling rod (4); and a pneumatic control unit for alternating impinging of compressed air upon the pressure chambers, characterized in that to maintain the functioning of the diaphragm pump above a pressure ratio of 1:3 of ambient pressure to product pressure in the area of the pressure pump chambers (1, 2), a rigid supporting disc is inserted between the end of the coupling rod 4 and the inner side of the membrane (5) onto the dog (18), having a diameter which corresponds to between 50% and 95% of the diameter of the working surface of the membrane, wherein its periphery is formed as a rounded shoulder (21) which is facing away from the membrane body (15).
 23. The high pressure membrane pump according to claim 22, characterized in that during the operation, the pump is operated with a pressure ratio of the air pressure to product pressure in a range of 1:3 to 1:6.
 24. The high pressure membrane pump according to claim 22, characterized in that the diameter of the supporting disc (20) corresponds to between 70% and 85% of the diameter of the working surface of the membrane.
 25. The high pressure membrane pump according to claim 24, characterized in that the diameter of the supporting disc (20) is greater than the diameter of the implant body.
 26. The high pressure membrane pump according to claim 25, characterized in that the diameter of the supporting disc (20) corresponds to 150% to 210% of the diameter of the implant body.
 27. The high pressure membrane pump according to claim 22, characterized in that the supporting disc (20) is provided with a central opening (22) which permits movement of the dog (18) in the direction of the movement axis (A) of the coupling rod (4).
 28. The high pressure double membrane pump according to claim 22, characterized in that the shoulder (21) originates from a flat central area of the supporting disc (20) and ends with a partial circle in profile.
 29. The high pressure double membrane pump according to claim 28, characterized in that the partial circle of the shoulder ends in an inclined surface, wherein—seen in the profile—a tangent is formed to the inclined surface, which forms in its endpoint an angle from 20 degrees to 60 degrees to the movement axis of the coupling rod.
 30. The high pressure double membrane pump according to claim 22, provided with a membrane body (15) which is curved inwardly toward the air chamber with a saucer shape, wherein the supporting disc (20) is inserted in the concave area of the membrane curve, and the outer ring area of the membrane presses around the shoulder (21) when impacted by pressure.
 31. The high pressure double membrane pump according to claim 22, characterized in that the supporting disc is provided with cutouts or material reductions.
 32. The high pressure double membrane pump according to claim 22, characterized in that the outer side of the supporting disc pointing toward the membrane is smooth.
 33. A membrane element for a high pressure double membrane pump having a pressure ratio of air pressure to product pressure greater than 1:3, in a functional high pressure double membrane in which one of the pump chambers is divided into a product chamber and an air pressure chamber having changing volume, comprising the actual membrane provided with a peripherally mounted elastomer body, wherein a rigid implant body is embedded in the central region of the membrane body which is provided with a dog connected with one end to the coupling rod, comprising a rigid supporting disk, which is mounted between the end of the coupling rod and the inner side of the membrane on the dog, having a diameter which corresponds to between 50% to 95% of the diameter of the working surface of the membrane, whose periphery is formed as a rounded shoulder that is turned away from the membrane body.
 34. The member element according to claim 33, characterized in that the diameter of the supporting disc corresponds to 150% to 210% of the diameter of the implant body.
 35. The membrane element according to claim 33, characterized in that the shoulder originates from a flat central area of the supporting disc and ends with a partial circle, which ends in an inclined surface, wherein—seen in profile—a tangent is formed to the inclined surface which forms in its end point an angle of 20 degrees to 60 degrees to the movement axis of the coupling rod.
 36. The membrane element according to claim 33, provided with a saucer-shaped membrane body curved toward the air chamber, characterized in that the supporting disc is inserted in the concave area of the membrane cure and presses onto the outer ring area of the membrane when impacted by pressure. 